1. Field of the Invention
The present invention relates to a method for defining a shape by a CAD system, defining machining by a CAM system, and making computation for a cutter path for the shape machining, thereby originating NC data, and more particularly, to a CAD/CAM system by which a cutter path for a modified shape can automatically be recreated on the CAM side immediately when the shape is modified by the CAD.
2. Description of the Related Art
The CAD (Computer-Aided Design) system and CAM (Computer-Aided Manufacturing) system have been developed and advanced separately. Referring to FIG. 1, in order to integrate these two systems, therefore, graphic data of which shapes were defined by a CAD system 1 is delivered to a CAM system after being first transformed into intermediate data 3 represented in a format such as IGES (Initial Graphics Exchange Specification) or DXF (Drawing Interchange File), as shown in FIG. 1. Based on this intermediate data 3, the CAM system makes computation for a cutter path and the like, thereby originating NC data and other data. In FIG. 1, M1 designates a memory in the CAD system 1, which is stored with the graphic data and the like originated by the CAD. Further, M2 designates a memory in the CAM system 2, which is stored with the graphic data, NC data, etc. originated by the CAM system 2.
As described above, the CAD side and the CAM side are coupled by the intermediate data, so that the CAM system 2 can learn the graphic data defined by the CAD system 1, but, it cannot be informed of any contents of the operation such as modification that the CAD system has executed afterward for the graphic form.
On the other hand, a computer system is generally provided with a customizing function (that is, a function which enables a user to add functions and the like). Accordingly, the CAD system is also provided with the customizing function. The use of this customizing function obviates the necessity of the intermediate data 3 for the transfer of the graphic data between the CAD system and the CAM system, and enables the CAM system 2 to access the data base of the CAD system 1.
FIG. 2 is a block diagram showing a CAD/CAM system in which the CAD system 1 has the aforesaid customizing function and then requires no use of the intermediate data 3. In this case, the CAD system 1 is additionally provided with a customizing function 4, and the CAM system 2 can directly access the data base of the CAD system 1 and make computation for a cutter path, thereby originating the NC data, by utilizing the customizing function 4. As shown in FIG. 2, the memory M1 of the CAD system 1 is loaded with the graphic data defined by the CAD system 1 and the NC data originated on the side of the CAM system 2, while the memory section M2 of the CAM system is loaded with data for machining definition defined in order to originate the NC data and the originated NC data.
In originating the NC data by a conventional CAD/CAM system such as the one shown in FIG. 2, when the graphic form is modified by the CAD system 1 after the NC data has been created, disagreement naturally occurs between the modified graphic form and the cutter path unless an operator gives a command for recomputation of the cutter path in accordance with the modified graphic form. Thus, there is a possibility that machining is erroneously effected by the unmodified NC data, despite the modification of the graphic form.
Referring now to FIGS. 4(a)-4(c) showing states displayed on a CRT display screen, the conventional procedure of operation covering from the definition of the graphic form by the CAD system to the NC data origination by the CAM system will be described.
First, the shape of an object of machining is defined by the CAD system 1. In the example shown in FIG. 4, four spline curves with ID codes entID1 to entID4 are first defined. A curved surface srfID1 is then formed through combination of these four curves and the curved surface srfID1 is then assigned an ID code. Thereupon, the curved surface srfID1 composed of the four spline curves entID1 to entID4 is displayed on the CRT screen, as shown in FIG. 4(a). Then, the graphic data are delivered to the CAM system 2.
When the CAM system 2 to receives the graphic data having the assigned ID codes, on the other hand, the shape of the curved surface srfID1 is drawn on the CRT screen of the CAM system 2, as shown in FIG. 4(b). If the definition of the machining is selected on the CRT screen, an input command picture for machining conditions appears in a window form, and an accessible state for input is established. When data for the machining definition, including the tool feed speed, starting point of machining, pitch, tool shape, cutting path pattern, etc., and a cutter path computation command are inputted, the CAM system 2 computes a cutter path pas1 in accordance with the inputted conditions and displays it on the CRT screen, as show in FIG. 4(c). As the cutter path pas1 is computed, the NC data are originated.
When the graphic form is modified by the CAD system 1 after the cutter path is computed to originate the NC data in the manner described above, this naturally causes a phenomenon that the modified graphic form disagrees with the cutter path data and NC data unless commands are given again for cutter path computation and NC data origination.
FIGS. 5(a) and 5(b) are diagrams for illustrating this situation. As shown in FIG. 5(a), when the cutter path computation is completed for the curved surface srfID1 cutter path pas1 is displayed on the CRT screen of the CAM system 2 graphic form is then modified into srfID1' from srfID1 by the CAD system and then displayed on CAM system 2, as shown in FIG. 5(b), there will be disagreement between the graphic data (curved surface data) and cutter path pas 1. This causes thereby an inconsistency between these data. In order to eliminate this inconsistency, the cutter path computation must be executed again in accordance with the modified graphic data, i.e. the cutter path computation command must again be applied to the CAM system after inputting the modified graphic data by using the CRT input command picture.